Many different types of printing equipment are used to process various types of documents. For example, banks and similar establishments use printing equipment designed to handle specific types of documents such as standard checks. In processing such checks, it is most often desired to print a series of characters or coded distinguishing marks thereon as a means of identification for the bank. The printing of the characters or distinguishing marks on the document is performed by moving the documents through a printing device or apparatus where marking occurs. The documents may be supplied to the printer by a document feeder which pulls the documents one by one from a storage area and supplies the documents to the printer.
Several document feeders are known where turning wheels pull the document to a guide through which the document passes. In such feeders, a series of documents are stored or stacked in a tray. The stack of documents rest on a set of initial pull wheels or rollers. When the wheels or rollers turn the bottom document of the stack is moved or pulled out of the stack. The document is passed to other rollers that continue the pull and which only permit the massage of a single document. The document is discharged toward the printing station where printing on the document will occur. A motor driven drive and/or gear system is provided with such systems for starting and stopping the movement of the pull rollers as necessary to accomplish the above-identified operation.
There are a number of disadvantages with these types of devices. In such devices, the tray or plate that supports the stack of documents to be processed is pressed toward the pull wheels by a spring or similar device. As a result, when the stack of documents is of considerable height, the push achieved by the spring is high. However, when the stack of documents becomes low, the push of the spring is reduced by a cOnsiderable amount. The pressure on the pull wheels exerted by the document stack differs, therefore, depending on the number of documents stacked. As a result, the pressure exerted by the device on the pull wheels differs for each document which is pulled by the pull wheels. Additionally, such feeders are intended to process documents of a specific length and are unable to adapt to documents of different length.
Another disadvantage of such feeders is that the selection means which allow only one document to pass through the guide at a time is most typically comprised of a single pair of tangential rollers. Selection of the single document, is achieved, therefore along a line which is the tangent to both rollers. Such a configuration is disadvantageous and may result in a reduced effectiveness of the selection means.
The document feeder proposed by the invention has been designed to fully resolve these problems, offering for that purpose a simple, effective structure in operation and purpose.